Several proteins in this family form iron-sulfur clusters enabling iron dependent DNA transcription regulation [1]. The iron binding is mediated by three conserved cysteine residues. Members of this family can also bind O-acetyl-L-serine, [Fe-S] and nitric oxide (Matilla et. al., FEMS Microbiology Reviews, fuab043, 45, 2021, 1. https://doi.org/10.1093/femsre/fuab043).

1: Studies of IscR reveal a unique mechanism for metal-dependent regulation of DNA binding specificity. Rajagopalan S, Teter SJ, Zwart PH, Brennan RG, Phillips KJ, Kiley PJ; Nat Struct Mol Biol. 2013;20:740-747. PMID:23644595